Regeneration of metal halide catalyst

ABSTRACT

A process for regenerating metal halide catalysts deactivated in hydroconversion of nitrogen-containing feedstocks by the formation of metal halide-ammonium halide complexes is disclosed. Regeneration is effected by contacting the complex with an electron donor solvent for metal halide at conditions at which the solvent effects decomposition of the complex and separation of the resultant metal halide and ammonium halide decomposition products by dissolving the metal halide.

United States Patent Kiovsky et al. [45] Apr. 18, 1972 [541 REGENERATION0F METAL HALIDE 3,355,376 11/1967 Gorin et al ..208/l0 CATALYST3,371,049 2/1968 Gorin et al ..208/l0 [72] Inventors: Thomas E. Kiovsky,El Sobrante; Wiltried Primary Examiner Delben E Gamz Penny Berkeley bothof Calif Assistant Examiner-Veronica O'Keefe [73] Assignee: Shell OilCompany, New York, NY. Attorney-Glen R. Gruenewald and Harold L. Denkler[22] Filed: Apr. 27, 1970 ABSTRACT N 1 [21] Appl o 3 882 A process forregenerating metal halide catalysts deactivated in hydroconversion ofnitrogen-containing feedstocks by the U.S. f nati n of meta] ha]ideammonium cgmplexes is dis. -Cl0g1/06 closed. Regeneration is effected bycontacting the complex [58] Field Search 308/10 108; 252/413 414 with anelectron donor solvent for metal halide at conditions i d at which thesolvent effects decomposition of the complex and [5 6] References C mseparation of the resultant metal halide and ammonium halide UNITEDSTATES PATENTS decomposition products by dissolving the metal halide.

3,542,665 11/1970 Wald ..208/l0 14 Claims, 2 Drawing Figures SbBr t 23's SECOND CONDENSING ZONE AROMATICS SEPARATOP 21 CH;

' k I90 24 H2 PRODUCT SbBr 200 20 HRST NH3 13 CONDENSING 5 I AROMATICS20V 8, ZONE k CH4 +I7 CH4 AROMATICS N \le 3 i" HYDRO 9 EXTRAC- DECOMPO-'8 2 13 CONVERSION 7 TION tb i L'Z CHAR gg i Ne ZONE sbBrg, ZONE 2 0 ASHCOAL 2 (NH4lgSbBr CHAR x Sb CHAR 011. 2: ASH ASH CHAR Sb SbBrREGENERATION OF METAL HALIDE CATALYST BACKGROUND It has been found thatcertain metal halides when employed asa continuous phase at temperaturesin the range of 350 C and under hydrogen pressure are excellentcatalysts for converting heavy hydrocarbons and similarmaterials such ascoal into useful low boiling hydrocarbons such as gasoline. Typical ofthese metal halides are antimony tribromide, antimony triiodide, zincchloride, zinc bromide, zinc iodide, mercuric iodide, cadmium iodide,gallium bromide, bismuth tribromide, bismuth triiodide, tin chloride,tin bromide, tin iodide and arsenic iodide.

Most of the above-mentioned metal halides are excellent catalysts thatresist deactivation by such materials as sulfur and oxygen that arebound in organic molecules found in many materials that may be convertedby such a process, and by their reaction products, and additionally themetal halide catalysts are not deactivated by ash that is found in coal,coke or char that results from high temperature reactions of the charge,metals such as nickel and vanadium that are found in residual petroleumfractions, and other such materials. However, the metal halide catalystsare deactivated by ammonia formed by hydrogenation of organically boundnitrogen found in many feeds to such a process, especially in coal.Deactivation by ammonia has been found to be partly due to the formationof stable ammonium halide-metal halide complexes having the generalformula (NH.,),,MX,, where X is a halogen, M is a metal, and a and b arewhole numbers.

Although the complex is not literally a catalyst poison, it causes aloss of catalyst activity by dilution and by removing the metal halidefrom the bulk material as an active catalytic agent. A continuous phasemetal halide catalyst can function with a large quantity of complex init, but as the complex builds up to significant quantities, the catalystactivity drops off.

Regeneration of the metal halide catalyst by recovering the metal halidefrom the complex is important if a continuous conversion process is tobe economically effected. Prior attempts to restore the metal halideinvolved oxidation of the ammonium portion of the complex to water andnitrogen whereby the metal halide was released from the complex.However, this is a high temperature process and it is difficult toeffect as well as being accompanied by undesirable side reactions.

THE INVENTION This invention includes the discovery that decompositionof the ammonium halide-metal halide complex and separation of the metalhalide may be accomplished readily and almost completely by contactingthe complex with an electron donor solvent, that is, a solvent that hasan unshared electron pair, which solvent not only causes decompositionof the complex into ammonium halide and metal halide but effectsseparation of the metal halide from the ammonium halide by selectivelydissolving the metal halide. Examples of such electron donor solventsare ketones, nitriles, ethers, alcohols, esters, glycols, organic acids,heteroatomic petroleum fractions such as pitch, mixtures rich inpolynuclear aromatics such as heavy gas oils derived from petroleum orcoal, and mixtures such as benzene-methanol and diethylether-methanol.

The efficiency of an electron donor solvent in this invention, both withregard to the amount of complex that may be converted and the rate ofconversion, appears to be related to the asymmetry and polarity of thesolvent molecules and to the temperature of contact between the complexand the solvent. Qxygencontaining solvents such as acetone, methylethylketone and methanol quickly effect decomposition of the complex atrelatively low temperature. Less heteroatomic materials such as pitchand heavy gas oils are not as effective as the oxygenated solvents, butthey can be used at substantially higher temperatures to obtainequivalent results, and the resultant solution of metal halide in pitchor gas oil may be charged directly to a hydroconversion zone therebyavoiding the need to separate metal halide from solvent and solventlosses.

Although the essence of the invention is contacting the ammoniumhalide-metal halide complex with an electron donor solvent to causedecomposition of the complex and separation of the metal halide from theresultant ammonium halide, various preferred embodiments of theinvention refine the basic reaction to make it much more efiicient andeconomical. in some embodiments it has been found that the electrondonor solvent may be used much more efficiently if the catalyst from thehydrotreating zone is first extracted with aromatics to remove metalhalide that has not been complexed and oil from the reaction zone beforethe catalyst stream is contacted with the electron donor solvent. Suchinitial extraction removes metal halide andoil from the catalyst streamand returns it directly to the reaction zone while only that portion ofthe stream from the hydroconversion zone representing impurities such asthe ammonium halide-metal halide complex, ash, char, metals, etc., issubjected to contact with the electron donor solvent.

Another advantageous embodiment of this invention is reacting theammonium halide separated from the complex to form hydrogen halide andammonia. Hydrogen halide is an oxidizing agent that may be employed inthe hydroconversion zone to prevent reduction of metal halide to metalor it may be employed in a separate oxidizing zone to oxidize reducedmetal to the metal halide which may be returned to the reaction zone. Indecomposing ammonium halide to form hydrogen halide, ammonia is alsoformed and it may be recovered as a separate product.

Following are several examples which illustrate the process of thepresent invention and are presented here as illustrative of theinvention without intending to limit its scope. In all cases, the metalhalide was employed to hydroconvert Illinois No. 6 coal or Big Horn coalinto clean hydrocarbons boiling largely in the gasoline boiling rangeand being substantially free of oxygen, nitrogen, sulfur, and metalimpurities as well as being separated from the ash that was contained inthe coal. The reaction is effected by introducing finely ground coalinto a continuous phase metal halide melt within a reaction zone whileunder hydrogen pressure and recovering from the reaction zone thenormally liquid hydrocarbons produced as well as various vapor phasematerials including normally gaseous hydrocarbons, hydrogen sulfide,water vapor, ammonia and hydrogen gas. The coal may be slurn'ed in pitchor other hydroconvertible liquid or in recycle salt. Ideally, thehydrogen gas is separated from the other vapor phase materials andreturned to the reaction zone while the hydrocarbon product is separatedfrom the water, hydrogen sulfide and ammonia impurities, separated intofractions and employed or further treated as appropriate.

In the conversion of coal as above indicated, some of the ammonia reactswith the metal halide to form an ammonium halide-metal halide complexthat represents both a loss of catalyst and a dilution of the catalystso that the catalyst activity ultimately is affected when significantamounts of the complex are present. Additionally, solids resulting fromthe reaction, typically ash from the coal and char from unconvertablecarbonaceous materials in the coal accumulate in the liquid phasecatalyst and these materials also reduce catalyst activity by dilution.In order for a continuous hydroconversion process to be effected it isnecessary that the catalyst be removed from the continuous phase andfresh metal halide be added to the continuous phase, and for the processto be economical it is necessary for the metal halide to be recoveredfrom the complex and returned to the hydroconversion zone. The followingtable is provided to illustrate the conditions under which suchregeneration may be effected.

It may be seen from the table that a wide variety of electron donorsolvent may be used to convert ammonium bromide-antimony bromide complexto antimony tribromide and ammonium bromide. In all cases the antimonytribromide is soluble in the solvent and is separated from insolubleammonium Convcr- Solvent/ Tcmpersion, complex ature, mole we ght(.umplhx Holvent C. percent ratio (N lhhflhlirs. Acetone 56. 2 70. 7 1.2 (Nnmsbun Methyl ethyl ketone 79. 6 68. 7 2. (N lldzSbBrs Methanol 2575 3.0 (N llOzSbllrr Methanol-methyl 25 75 3.0 (N H4) :Sb BraTetrahydroluran 64 100 8. 9 (NHmSbBrs. Acetonitrile. 80.1 70. 4 31. 4(NHOQSbBl's Benzonitrile 190. 7 100 25 (NIIOzSbBls. West Texas flasherpitch. 350-390 60. 2 3.0 (NHDeSbBra Catalytic cracked gas oil. 270-28046. 8 38 (NHOaSbBrs 1 Coker gas oil 260-270 40. 5 38 (NHQzSbBrs .do270-305 45. 7 43 (NHQgZnBn... Acetone 56.2 40.8 7.7 (NHQzZnBn... Methylethyl ketone 79. 6 52.3 8. 4 (NHmZnCh Acetone 56. 2 25.9 7. 7

bromide upon decomposition of the complex. It may also be pointed outthat the wide variations in weight ratio between solvent and complex arenot as significantly different on a mole basis because the heavyhydrocarbon fractions used have a relatively high molecular weightcompared to the oxygencontaining solvents reported in the table. The useof large quantities of material that is going to be charged to thehydroconversion process is not detrimental because a subsequentseparation of antimony bromide from solvent is not necessary.

The table also illustrates that the process of this invention iseffective to decompose other ammonium halide-metal halide complexes.Equivalent but not identical results are obtained with other metalhalides such as zinc iodide, cadmium iodide, bismuth bromide or iodideand others.

The process of the present invention may be best describe with referenceto the accompanying drawings which are highly schematic flow diagrams ofprocesses embodying this invention. The flow diagrams employ boxesillustrating various functions and no attempt is made to show valves,controls, vessel or other conventional equipment ordinarily employed foreffecting the various functions defined.

FIG. 1 is a flow diagram of a process embodying this invention employinga circulating solvent that is not hydroconverted, while FIG. 2 is a flowdiagram of a process employing a oncethrough solvent.

Referring to FIG. 1 a process for hydroconversion of coal to liquidhydrocarbons is described employing antimony tribromide as a catalyst.The process illustrated in the drawing is effected by maintaining acontinuous phase of antimony tribromide in hydroconversion zone 1 andadding coal through line 2 and hydrogen through line 3 as charge to thehydroconversion zone. After a continuous phase of catalyst is introducedinto hydroconversion zone 1, only irretrievable losses of fresh catalystare introduced through line 4 to maintain the catalyst capacity of thesystem while recycle material including antimony tribromide is returnedto hydroconversion zone 1 from downstream processing via line 5 and line4. The hydroconversion of coal effected in zone 1 results in theproduction of liquid hydrocarbons which are removed throughline 6 alongwith hydrogen and other vapor phase materials produced in the processsuch as water, ammonia and hydrogen sulfide.

To maintain the catalyst activity a portion of the liquid phase materialin hydroconversion zone 1 is withdrawn through line 7 and passeddirectly, or indirectly, to extraction zone 8. The material in line 7includes antimony tribromide catalyst and oil which are necessarilywithdrawn from hydroconversion zone 1 in that separation of variousmaterials from one another cannot be adequately effected therein, aswell as ammonium bromide-antimony bromide complex, ash, char, andperhaps some antimony metal if conditions in the hydroconversion zoneare such that antimony tribromide is reduced. As will be discussedhereinafter, when antimony metal is present in the material in line 7 analternative processing route may be taken, but when antimony metal isnot present in the material, line 7 discharges into extraction zone 8.

ln extraction zone 8 the material from line 7 is contacted with a streamof aromatics or other suitable solvent for antimony tribromide and oilintroduced through line 9. This solvent is not for the purpose ofdecomposing the complex but for selectively dissolving antimonytribromide and oil. The extracted material passes from separation zone 8through line .10. The material not extracted which includes ammoniumbromide-antimony bromide complex, ash, and char is removed fromextraction zone 8 through line 11. The antimony bromide, oil andaromatic mixture in line 10 passes into separation zone 12 where asimple fractionation separates the aromatics from the antimonytribromide and oil, the latter materials being passed to line 5 andultimately returned to hydroconversion zone 1 while the aromatics passthrough line 14 into line 9 and are returned to extraction zone 8.

The material in line 11 passes to regeneration zone 15 wherein it iscontacted in one or more stages with an electron donor solvent such asacetone introduced through line 16. The electron donor solventdecomposes the ammonium bromideantimony bromide complex and dissolvesthe antimony bromide. The undissolved ammonium bromide, ash and char arewithdrawn from regeneration zone 15 through line 17. The solution ofantimony bromide in the acetone solvent is withdrawn from zone 15through line 18 and introduced into separation zone 19 in whichseparation of the acetone from the antimony bromide may be effected byfractionation. The antimony bromide resulting from the decomposition ofthe complex in regeneration zone 15 is passed from separator 19 throughline 20 into line 5 and ultimately returned to hydroconversion zone 1while the acetone is removed through line 21 and returned toregeneration zone 15 for further contact with the complex.

For the most part, the process of the present invention is successfullycompleted at this point and the material in line 17 may be discarded orthe ammonium bromide recovered for some other use. However, aparticularly advantageous modification of the process is to introducethe material from line 17 into a stripper 22 where the material isheated and a stripping gas shown herein as methane is introduced throughline 23 to strip the ammonium bromide from the ash and char. The ash andchar are removed through line 24 to be disposed of while ammoniumbromide and methane stripping gas are passed through line 25 intodecomposition zone 26. Methane is separated from ammonium bromide andreturned via line 29 into line 23 to effect further stripping ofammonium bromide in zone 22 while a suitable reactant, shown here assulfuric acid, is introduced into zone 26 through line 27 wherein itreacts with ammonium bromide to produce ammonium sulfate and hydrogenbromide. The hydrogen bromide is withdrawn from zone 26 through line 28and introduced into line 5, and ultimately into hydroconversion zone 1unless the aforementioned alternative to deal with antimony metal isemployed and the ammonium sulfate produced in zone 26 is removed throughline 30.

The hydrogen bromide produced in zone 26 preferably is introduceddirectly into hydroconversion zone 1 wherein its oxidizing effectprevents the formation of antimony metal by preventing reduction of theantimony bromide. However, if the presence of hydrogen bromide in thehydroconversion zone is undesirable for some reason, such as increasingthe catalyst activity to too great an extent, it may be used to oxidizeany antimony metal that might be formed in the hydroconversion zone.When antimony metal is formed in the hydroconversion zone it will passfrom zone 1 through line 7 and, as shown with broken lines, the streamfrom line 7 may be passed through line 31, oxidizing zone 32, and line33 to return it to line 7 and introduction into extraction zone 8. Thematerials in line 31 are contacted in oxidation zone 32 with hydrogenbromide that is generated in zone 26 and introduced into zone 32 throughline 34. In oxidation zone 32 the antimony metal present in the materialpassing from hydroconversion zone 1 is oxidized to antimony tribromidewith the evolution of hydrogen that is released through line 35. Theresultant material from zone 32 is passed through line 33 and ultimatelyinto extraction zone 8 wherein it is treated as hereinbefore described.The hydrogen generated in zone 32 is passed through line 35 and eitherreturned to the process or otherwise disposed of. Oxidation of antimonymetal may also be effected by contacting it with ammonium bromide orwith the antimony bromide-ammonium bromide complex under appropriateconditions.

FIG. 2 illustrates a particularly advantageous embodiment of thisinvention that may be employed if pitch or other heavy liquid phasematerial is a portion of the charge and an electron donor solvent aswell. In FIG. 2 a hydroconversion zone 41 is charged with pitch and coalthrough lines 42 and 43, respectively, hydrogen through line 44 and zinciodide catalyst through line 45. Again it is contemplated that line 45will supply only irretrievable losses of catalyst.

Hydrogen and product are withdrawn from hydroconversion zone 41 throughline 46 and a slipstream of the liquid catalyst phase is withdrawnthrough line 47. Line 47 will carry a mixture including zinc iodidecatalyst, oil, ammonium iodide-zinc iodide complex, ash, and char.

Line 47 discharges into regeneration zone 48 wherein its contents arecontacted with a stream of pitch passing from line 42 through line 49.As a result of the contact of the pitch and the material in zone 48, thecomplex is decomposed, the zinc iodide in zone 48 is dissolved in thepitch, the oil is dissolved in the pitch, and the undesired ash, charand ammonium iodide are rejected from the pitch phase and removedthrough line 51. The pitch, carrying dissolved oil and zinc iodide init, is passed through line 50 and returned to the charge stream in line42. It will usually be desirable to separate ammonium iodide from thestream in line 51 and to employ it as such or decompose it to ammoniaand hydrogen iodide, the latter product being returned tohydroconversion zone 41.

We claim as our invention:

1. The process for regenerating metal halide from metal halide-ammoniumhalide complex which comprises contacting the complex with an electrondonor solvent for metal halide at a temperature below the thermaldecomposition temperature of the metal halide but at which chemicalreaction with the solvent causes said complex to decompose whereby thecomplex decomposes and metal halide is preferentially dissolved in thesolvent and at least partly separated from the resultant ammonium halidedecomposition product.

2. The process of claim 1 wherein the electron donor solvent is aketone.

3. The process of claim 1 wherein the electron donor solvent is anester.

4. The process of claim 1 wherein the electron donor solvent is analcohol.

5. The process of claim 1 wherein the electron donor solvent is anitrile.

6. The process of claim 1 wherein the electron donor solvent is anether.

7. The process of claim 1 wherein the electron donor solvent is anorganic acid.

8. The process for hydroconversion of a nitrogen-containing carbonaceousmaterial which comprises contacting the carbonaceous material with acontinuous phase of a molten metal halide catalyst at conversionconditions and under hydrogen pressure in a hydroconversion zone,withdrawing a portion of the molten catalyst containing metal halide,ammonium halide complex from the hydroconversion zone and contacting itwith an electron donor solvent for metal halide at a temperature belowthe thermal decomposition temperature but at which chemical reactionwith the solvent causes said complex to decompose whereby the complexdecomposes and the metal halide is preferentially dissolved in thesolvent and at least partly separated from the resultant ammonium halide9. The process of claim 8 wherein the electron donor solvent is a heavyliquid hydrocarbon fraction, and the solvent with metal halide dissolvedtherein is introduced into the hydroconversion zone.

10. The process of claim 9 wherein the electron donor solsmig t h-wflmh.

11. The process of claim 8 wherein the ammonium halide is converted toammonia and hydrogen halide, and hydrogen halide is introduced into thehydroconversion zone.

12. The process of claim 1 wherein the metal halide is zinc halide.

13. The process of claim 1 wherein the metal halide is zinc chloride.

14. The process of claim 1 wherein the metal halide is zinc iodide.

2. The process of claim 1 wherein the electron donor solvent is aketone.
 3. The process of claim 1 wherein the electron donor solvent isan ester.
 4. The process of claim 1 wherein the electron donor solventis an alcohol.
 5. The process of claim 1 wherein the electron donorsolvent is a nitrile.
 6. The process of claim 1 wherein the electrondonor solvent is an ether.
 7. The process of claim 1 wherein theelectron donor solvent is an organic acid.
 8. The process forhydroconversion of a nitrogen-containing carbonaceous material whichcomprises contacting the carbonaceous material with a continuous phaseof a molten metal halide catalyst at conversion conditions and underhydrogen pressure in a hydrOconversion zone, withdrawing a portion ofthe molten catalyst containing metal halide, ammonium halide complexfrom the hydroconversion zone and contacting it with an electron donorsolvent for metal halide at a temperature below the thermaldecomposition temperature but at which chemical reaction with thesolvent causes said complex to decompose whereby the complex decomposesand the metal halide is preferentially dissolved in the solvent and atleast partly separated from the resultant ammonium halide decompositionproduct.
 9. The process of claim 8 wherein the electron donor solvent isa heavy liquid hydrocarbon fraction, and the solvent with metal halidedissolved therein is introduced into the hydroconversion zone.
 10. Theprocess of claim 9 wherein the electron donor solvent is pitch.
 11. Theprocess of claim 8 wherein the ammonium halide is converted to ammoniaand hydrogen halide, and hydrogen halide is introduced into thehydroconversion zone.
 12. The process of claim 1 wherein the metalhalide is zinc halide.
 13. The process of claim 1 wherein the metalhalide is zinc chloride.
 14. The process of claim 1 wherein the metalhalide is zinc iodide.